A 26-year-old man from a Boston suburb was arrested on Wednesday and accused of plotting to attack the Pentagon and the U.S. Capitol with remote-controlled model planes packed with explosives.

The FBI said Rezwan Ferdaus hoped to use military-jet replicas, 5 to 7 1/2 feet long, guided by GPS devices and capable of speeds over 100 mph.

Remote-controlled aircraft have been considered by terrorists before. In 2008, Christopher Paul of Worthington pleaded guilty to plotting terrorist attacks in the United States and Europe using explosive devices. Prosecutors said he researched remote-controlled boats and a remote-controlled 5-foot-long helicopter.

Federal officials have long been aware of the possibility that someone might try to use such planes as weapons, but there are no restrictions on their purchase. Ferdaus is said to have bought his over the Internet.

Counterterrorism experts and model-aircraft hobbyists said it would be nearly impossible to inflict large-scale damage of the sort that Ferdaus allegedly envisioned. The aircraft are too small, can’t carry enough explosives and are too tricky to fly, they said.

“The idea of pushing a button and this thing diving into the Pentagon is kind of a joke, actually,” said Greg Hahn, technical director of the Academy of Model Aeronautics.

Rick Nelson, a former Navy helicopter pilot who is now a senior fellow at the Center for Strategic and International Studies, said Ferdaus would have had to hit a window or other vulnerable area to maximize damage, and that would have taken precision flying.

“Flying a remote-controlled plane isn’t as easy as it looks, and then to put an explosive on it and have that explosive detonate at the time and place that you want it, add to the difficulty of actually doing it,” he said.

Ferdaus, a Muslim American, was arrested after federal agents posing as al-Qaida members delivered what he thought was 24?pounds of C-4 explosive, authorities said. He was charged with attempting to damage or destroy a federal building with explosives.

A federal affidavit says he began planning “jihad” against the United States in early 2010 after becoming convinced through jihadi websites and videos that America was evil.

Ferdaus had a physics degree from Northeastern University and enjoyed “taking stuff apart” and “ learning on my own,” according to court papers.

The model planes Ferdaus considered were the F-4 Phantom and the F-86 Sabre — small-scale versions of military jets, investigators said. The F-4 is the more expensive of the two, at up to $20,000, Hahn said. The F-86, one of which Ferdaus actually obtained, costs $6,000 to $10,000 new.

Ferdaus’ plan, as alleged in court papers, was to launch three planes from a park near the Pentagon and Capitol and use GPS to direct them toward the buildings, where they would detonate on impact and blow the Capitol dome to “smithereens.” He planned to pack 5 pounds of plastic explosives on each plane, according to prosecutors.

James Crippin, an explosives and anti-terrorism expert, said that much C-4 could do serious damage — a half-pound will obliterate a car. But he said getting a stable explosive like C-4 to blow up at the right time would have been hugely difficult.